安燕飞,陈凯鑫,王亚乔,程硕,黄楗,何舒扬,王胜建
AN Yanfei,CHEN Kaixin,WANG Yaqiao,CHENG Shuo,HUANG Jian,HE Shuyang,WANG Shengjian

• 1:安徽大学资源与环境工程学院
• 2:安徽大学材料科学与工程学院
• 3:中国地质调查局油气资源调查中心

摘要(Abstract)：

天然焦内炭微球是煤层遭受岩浆速热变质的产物，其显微光学特征成因解析有助于深入认识煤速热碳化和热变质。采集安徽淮北石台煤矿富含炭微球的天然焦样品，利用高分辨率反射偏光显微镜和扫描电镜等实验手段，表征了天然焦中炭微球的粒度、分布、显微光学和超微组构特征，以揭示其光学各向异性的成因和热演化意义。结果显示，远离岩体天然焦中炭微球以粗粒为主，粒径10～100μm，少数可达150μm以上；紧邻岩体天然焦炭微球以细粒为主，粒径1～10μm，在岩体内脉状焦内甚至低至1μm以下。分析显示，粗粒炭微球和炭半球分别发育“十字”消光和“波状”消光，是其内部放射状一轴晶光率体在切面内投影的光学表征；细粒炭微球发育“十字-双曲线”消光，是其内部放射排布的二轴晶光率体切片投影的旋转效应。由此可见，趋近岩体，伴随着镜质体反射率增加，煤焦光率体逐渐由规则球形(光性均质体)，向二轴椭球体(一轴晶)和三轴椭球体(二轴晶)转变。在该过程中，“十字”消光和“波状”消光的粗粒炭微球是煤热脱挥发分的产物，而“十字-双曲线”消光的细粒炭微球是煤热缩聚而片层化的标志。天然焦中炭微球的显微光学特征是煤层趋热碳化的结果，本质上是其光率体受热变形的光学表征，可有效评价岩浆蚀变煤焦的热变质程度。
Carbon microspheres(CMs) in natural coke are formed when coal seams undergo magma-induced rapid thermal metamorphism. Analyzing the origin of the optical microscopic characteristics of CMs assists in gaining deep insights into the rapid thermal carbonization and metamorphism of coals. This study examined the natural coke samples rich in CMs from Shitai Coal Mine in Huaibei, Anhui Province. Using experiments like high-resolution reflected polarized light microscopy and scanning electron microscopy(SEM), this study characterized the particle sizes, distribution,optical microscopic characteristics, and ultramicrofabrics of CMs in natural coke, revealing the origin and thermal evolution implications of their optical anisotropy. The results indicate that the natural coke far from the rock masses is primarily composed of coarse-grained CMs with sizes ranging from 10 to 100 μm, and even above 150 μm in some cases. In contrast, the natural coke adjacent to rock masses predominantly comprises fine-grained CMs with sizes between 1 and10 μm. Additionally, the particle sizes of CMs are even below 1 μm in veined coke within rock masses. The analytical results indicate that coarse-grained CMs and carbon semispheres exhibit cross and wavy extinction, respectively, which are the optical characterization of radial uniaxial indicatrix when being projected onto the tangent plane. Fine-grained CMs manifest cross-hyperbolic extinction, which is the rotational effect generated when radial biaxial indicatrix inside are projected onto the sections. Hence, with a reduction in the distance from rock masses and an increase in vitrinite reflectance, indicatrix of coke gradually transitions from regular spheres(optically isotropic substances) toward biaxial ellipsoids(uniaxial crystals) and triaxial ellipsoids(biaxial crystals). During the transition, the coarse-grained CMs with cross-wavy extinction are the product of the thermal devolatilization of coals, whereas the fine-grained CMs with crosshyperbolic extinction are the sign of coal lamination formed by thermal polycondensation. The optical microscopic characteristics of CMs in natural coke, stemming from the thermal carbonization of coal seams, essentially represent the optical characterization of indicatrix subjected to thermal deformation. Therefore, these characteristics can be employed to effectively assess the thermal metamorphism degree of magma-altered coal coke.

关键词(KeyWords)： 炭微球;十字消光;光学各向异性;光率体;天然焦;安徽淮北石台煤矿
carbon microsphere(CM);cross extinction;optical anisotropy;optical indicatrix;natural coke;Shitai Coal Mine in Huaibei,Anhui Province

Abstract:

Keywords:

基金项目(Foundation): 国家自然科学基金项目(41602173,42272203);; 安徽大学创新训练项目(X20240179)

作者(Author): 安燕飞,陈凯鑫,王亚乔,程硕,黄楗,何舒扬,王胜建
AN Yanfei,CHEN Kaixin,WANG Yaqiao,CHENG Shuo,HUANG Jian,HE Shuyang,WANG Shengjian

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